my son took the trigger out of his bps 28ga for a cleaning and we can't figure out how to get it back in. Looked at a utube video where they install one on a 12 ga, but still can't get it to drop in. Whats the trick!!!

GOT IT! 2 am after a six pack! Had the half moon front hammer pivot pin 180 deg off. When this happens you can still get the front of the trigger in but the rear will not drop in so you discount this as the issue and blame the mag blocker rods. Used a piece of packing foam to help hold the mag rods is place then slide the mag rods back as far as they will go toward the butt. Trigger will drop right in with a little wiggle every time. You do not have to use a knife of screwdriver blade as is suggested on some of the videos out there.
If you have a BPS I suggest you print this and stick it in your manual!!!

PS If you ever decide to remove your trigger. THIS IS NOT LIKE A REMINGTON! Only need to knock out out the wider lower retaining pin. It will save you some further grief. The other pin is retains the lifter fork. If you remove it there is a sleeve that falls out into the receiver or on the floor if the gun is upright when you pull out the trigger.